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November 2008

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Subject:
From:
Graham Naisbitt <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Graham Naisbitt <[log in to unmask]>
Date:
Mon, 3 Nov 2008 00:12:02 +0000
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text/plain (124 lines)
Hi Techies

You might benefit from using the IPC-TM-650 2.4.35 and 2.4.43 thru 46  
test methods to control your paste prior to use on the line.

Although these are currently in review for lead-free, I have some info  
to share if it will help.

Graham Naisbitt
Co-Chair TM-650 Test Methods Sub-Committee

On 2 Nov 2008, at 19:53, john queen wrote:

> This is an interesting one can anyone share there DOE of paste  
> selection and printer setup
> ----- Original Message ----- From: "John Goulet"  
> <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Sunday, November 02, 2008 7:01 PM
> Subject: Re: [TN] Controlled RH% Versus Screenprinting Results
>
>
> The viscosity of the solder paste also varies greatly with  
> temperature change
> that is easier to control. I've had to resolve the same issue at other
> companies and currently resolving it in this building and layout  
> again.
> Here are some things to consider before spending $500K.
> 1. Is the Receiving Dock and Incoming area totally sealed off from  
> the SMT
> area. It is pretty hard to manage temperature and humidity control  
> with 10'
> doors open many times a day. In one factory we put up a frame and  
> sheet
> rock walls around the dock and another for the receiving area.  
> Problem gone.
> 2. Are the air handlers equipped with programmable thermostates. If  
> they
> aren't and they don't have the dehumidifier options in them then at  
> night they
> will blow in cool damp air because it is cool enough the air- 
> conditioner will be
> acting as a fan only. In the current factory we going to do this  
> before summer.
> Hopefully we'll also separate  our SMT area as stated in #1.
> 3. Try some of the newly released solder pastes. Indium just came  
> out with
> 6.3 WS tin/lead that is far better than the 6.2. Senju may not be  
> well known
> in the USA but in an extensive DOE they were the best for all  
> finishes. Senju is
> the #1 paste overseas.
> 4. The paste storage and handling in the productin line to prevent  
> the flux
> from separating is important. A low voume high mix shop may need to  
> buy
> 5000 gram or less and not the 7000 gram tubes since you can't put  
> them back
> in the refrigerator. Large beads of paste over 1/2" may be easier  
> for the
> operator but in higher humidity and temperature the paste on the  
> stencil is
> going to change for the worse. The paste spec is written for beads  
> up to 3/4"
> but that is in ideal RH and temp situations. Small factories that  
> weren't
> designed for this industry are prone to the same situation that you  
> have. One
> large factory had a huge sock like air exhange units that blew in  
> whatever air
> is outside. In the winter  you can have small humidifiers added but  
> in the rainy
> spring and humid summer you have to relay on using the best paste  
> and very
> good handling controls. Keep the jar low on the rack or floor since  
> since with
> air conditining the floor will be at a lower temperature  
> approximately 72F. The
> temperature in the machine it may reach 78-80 if you didn't add the  
> small fan
> for the summer months. In this way when the operator adds the paste  
> you'll
> stay in the middle of the control range.
>
>
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